1. Field of the Invention
The present invention relates in general to an electrical network in which analog signals are used to actuate a device such as a switch, pump or valve; and more particularly, to such an analog network used in activating devices in a pressurized light water nuclear power system.
2. Description of the Related Art
Many applications of electrical control systems require that the electrical control system be highly reliable. For example, whenever an electrical control system is operating in a hostile environment, such as in a nuclear power system or in outer space, the relability of such a control system is of paramount importance. Such reliability is commonly provided by some type of redundancy. Redundant controllers for an actuator are commonly connected in parallel and information is passed between them to prevent a system disturbance when control is switched from one controller to another. The usual method of selecting a controller is to use an electromechanical relay. While electromechanical relays are generally reliable, a relay can fail if its contacts have been damaged during "surge withstand tests", leaving no path for control of the actuator by any controller.